Interindividual variation in response to hydroxyurea treatment. Data are shown for 95 children with SCA treated at St Jude Children's Research Hospital, judged to be more than 80% adherent to hydroxyurea therapy. (A) Percentage HbF response, showing a broad distribution of percentage HbF values at hydroxyurea MTD, ranging from approximately 10% to more than 40%. (B) LDH response again showed a broad distribution of values at hydroxyurea MTD (normal < 310 U/L). Data analysis and graphs courtesy of Dr Cheng Cheng.